Silicon on insulator technology (SOI) refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing, for example, to reduce parasitic device capacitance and thereby improve performance. SOI-based devices differ from conventional silicon-built devices in that the silicon junction is above an electrical insulator, e.g., silicon dioxide.
A metal-oxide-semiconductor field-effect transistor (MOSFET) is a device that, for example, may be used to amplify or switch electronic signals. The MOSFET includes a channel of n-type or p-type semiconductor material, and is accordingly called an NMOSFET or a PMOSFET (also commonly known as nMOS, pMOS). For example, if the MOSFET is an n-channel or nMOS FET, then the source and drain are “n+” regions and the body is a “p” region. With sufficient gate voltage, above a threshold voltage (Vt) value, electrons from the source (and possibly also the drain) enter the inversion layer or n-channel at the interface between the p region and the oxide. This conducting channel extends between the source and the drain, and current is conducted through it when a voltage is applied between the source and drain.
The floating body effect is the effect of dependence of the body potential of a transistor realized by the silicon on insulator (SOI) technology on the history of its biasing and the carrier recombination processes. The transistor's body forms a capacitor against the insulated substrate. The charge accumulates on this capacitor and may cause adverse effects, for example, opening of parasitic transistors in the structure and causing off-state leakages, resulting in higher current consumption. The floating body effect also causes the history effect, which is a dependence of the threshold voltage (Vt) of the transistor on the transistor's previous states.
However, the floating body effect of an SOI MOSFET can shift threshold voltage (Vt) and/or increase Vt variation, which degrades integrated circuit (IC) yields. One countermeasure to floating body effect involves use of fully depleted (FD) devices. The insulator layer in FD devices is significantly thinner than the channel depletion width. The charge, and thus also the body potential, of the transistors is therefore fixed. However, the short-channel effect is worsened in the FD devices, i.e., the body may still charge up if both source and drain are high, such that the architecture is unsuitable for some analog devices that require contact with the body.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.